In a pushchair, the infant occupies a carrier. Such pushchairs are typically configured to enable releasable attachment of the carrier from the frame or chassis of the pushchair to enable multiple different carrier types (such as car seats, carrycots, etc.) to be used interchangeably.
Just as there are many variations in the combinations and styles of frames and carriers, there arc also many variations of wheel locking mechanisms known in the art typically a pushchair manufacturer/design house will design the frames or chassis of one or more of its pushchair offerings to include a proprietary wheel locking mechanism. In addition to being a point of differentiation from one brand of pushchair to another, pushchair manufacturers/design houses are continually looking to improve upon the performance of their own and other competing wheel locking mechanisms as to reliability, ease of use, cost, complexity, etc.